/* File: pgm4.c
   Programmer: Mark Fienup
   Homework assignment #4 with arrays
   October 2004
   Description: This program tallies the weekly sales for a mail-order house. 
   The mail order house sells five different products whose retail prices are
   stored in the array retailPrices.  The program should read a series of 
   product number and quantity sold pairs. A sentinel-value of -999 is used 
   for the product number to stop input.
*/

#include <stdio.h>
#define MAX_PRODUCT 5  // Total number of products

// function prototypes
void InitializePrices( float retailPrices[] );
void ReadProductsAndQuantities( int productQuantities[] );
void PrintSummary( float retailPrices[], int productQuantities[] );


int main() {

  float retailPrices[MAX_PRODUCT + 1];   // we'll waste element 0 
  int productQuantities[MAX_PRODUCT + 1] = {0};
  
  InitializePrices(retailPrices);
  ReadProductsAndQuantities(productQuantities);
  PrintSummary(retailPrices, productQuantities);

} // end main


/* This function initializes the retail prices in the array retailPrices.
   Product 1's price is at index 1, etc.
*/
void InitializePrices( float retailPrices[] ) {

  retailPrices[1] = 3.44;
  retailPrices[2] = 5.02;
  retailPrices[3] = 2.14;
  retailPrices[4] = 6.30;
  retailPrices[5] = 7.11;

} // end InitializePrices


/* This function reads the product # and quantity pairs from the user until a
   sentinel value of -999 is read.  The quantities of each product are tallied
   in the corresponding productsQuantities element, i.e., product 1's quantity
   tally is stored at productQuantities[1], etc.
*/
void ReadProductsAndQuantities( int productQuantities[] ) {

  int productNumber;    // Users choice number of what product
  int quantity;         // Number of units sold

  printf("Enter the a  product number (or -999 to quit):  ");
  scanf("%d", &productNumber);

  while (productNumber != -999) {

    if ( productNumber >= 1 && productNumber <= MAX_PRODUCT) {
      printf("How many were purchased? ");
      scanf("%d", &quantity);
      
      productQuantities[productNumber] += quantity;
    } else {
      printf("Product number must be between 1 and %d!\n", MAX_PRODUCT);
    } // end if
    
    printf("Enter the a  product number (or -999 to quit):  ");
    scanf("%d", &productNumber);
    
  } // end while
  
} // end ReadProductsAndQuantities


/* This function calculates and displays the total retail sales for 
   each products individually and the total overall sales.  
*/
void PrintSummary( float retailPrices[], int productQuantities[] ) {
  int index;
  double totalSales;

  totalSales = 0.0;
  printf("\n \n                SUMMARY OF SALES\n");
  for (index = 1; index <= MAX_PRODUCT; index++ ) {
  
    printf("There were %d Product %d's sold. Totaling $%.2f. \n\n", 
	   productQuantities[index], index,
	   productQuantities[index] * retailPrices[ index ] );
    totalSales += productQuantities[index] * retailPrices[ index ];
  } // end for

  printf("TOTAL SALES: $ %.2f \n", totalSales);

} // end PrintSummary